A day after the Padres placed Andrew Cashner on the 15-day disabled list with elbow soreness, manager Bud Black said the right-hander was feeling better. No definitive update, however, will come until after Cashner undergoes an MRI in San Diego on Monday.

For now, the extent of Cashner’s injury is unknown. Although Cashner had not shown a discernible dip in velocity in recent starts, one clue as to the cause of the soreness can be traced to his May 7 start against Kansas City.

In that outing, according to data tracked by PITCHf/x, Cashner did not throw a single slider among his 92 pitches. It was the first time in 40 career starts that he did not use the pitch.

Overall, too, it was Cashner’s rockiest start of the season. In the first inning alone, he threw 43 pitches, partly owing to a pair of errors by shortstop Everth Cabrera. He would exit after four innings, having allowed four runs, two earned, on seven hits and two walks.

Cashner made his next and latest start as scheduled, throwing seven innings of one-run ball against the Reds. He threw 95 pitches, including 25 sliders, according to PITCHf/x. Saturday, he recalled it as “probably one of the best starts as far as just my body and the way my arm felt.”

But on Thursday, about 48 hours removed from that start, he threw a side session and reported soreness the following day.

In nine starts this season, Cashner has relied more on his fastball (72.8 percent) than he did in 2013 (63.4 percent). His slider usage has also increased, from 14.4 percent to 18 percent, as he has employed it as an out pitch against left-handed hitters. Lefties are hitting .211 against the pitch, down from .229 last season.

He has almost completely shelved his curveball (0.9 percent, down from 2.9 percent).

Pitcher bats eighth

With Chase Headley getting his first start off since his return from the disabled list, the Padres on Sunday started Alexi Amarista at third base ... and batted him ninth.

Right-hander Donn Roach, who was making his first major league start and entered the day with a double in one career plate appearance, batted eighth. It was the first time a Padres pitcher batted anything but ninth since Kevin Correia hit eighth on June 21, 2009.

Padres manager Bud Black, sitting in his office before Sunday’s game, explained the rare lineup configuration: With Roach on a pitch count of roughly 60, the Padres planned on using a pinch-hitter relatively early in the game. By batting Roach eighth, the pinch-hitter would be able to hit one spot sooner than usual.

Roach would throw just 46 pitches in the Padres’ 8-6 loss. He was pinch-hit for by Will Venable in the top of the fourth.

Headley had started all seven of the Padres’ games since coming off the 15-day DL on May 10.

“He came back from the DL, and we thrust him right in there,” Black said. “I think this was a good time to give him a day off from starting the game.”

Meanwhile, Roach followed in the footsteps of not only Correia. In that 2009 series against Oakland, pitchers Wade LeBlanc, Walter Silva and Correia all started and batted eighth on consecutive days.